In the communication network such as a network mounted on a vehicle, in transmitting signals from one communication apparatus to other communication apparatus, there occurs a problem that owing to an electric noise or a magnetic noise, the transmission waveform distorts and that communication is not normally performed. The waveform distortion is generated owing to mainly the reflection of signals caused by impedance unmatching. The impedance unmatching is unavoidably generated at a branch point of a communication line and a connection point between the communication line and a substrate accommodated inside a communication apparatus. Therefore various arts for improving the waveform distortion at the branch point and the connection point between the communication line and the communication apparatus.
For example, in the art disclosed in Japanese Patent Application Laid-Open No. 6-76886 (patent document 1), as shown in FIG. 7, the terminal 2 accommodated inside the connector housing 1 is inserted through the cylindrical ferrite core 3 to improve the transmission waveform distortion.
Because the ferrite core 3 has an insulation property, electric current does not flow through the ferrite core 3 when the ferrite core 3 contacts the terminal 2. Thus the transmission waveform distortion can be improved.
But when a silicon steel plate or a permalloy which is a conductive magnetic material is used instead of the ferrite core 3, electric current flows through the silicon steel plate or the permalloy when the silicon steel plate or the permalloy contacts a terminal. Therefore the transmission waveform distortion cannot be improved.
As described above, the construction proposed in the patent document 1 has a problem that although it is possible to use the magnetic material such as the ferrite core having an insulation property as the filter material, it is impossible to use the conductive magnetic material such as the silicon steel plate or the permalloy as the filter material.
Patent document 1: Japanese Patent Application Laid-Open No. 6-76886